Some building types may be upgraded as replacements are researched.
Mana Pools may be upgraded to Mana Fountains.
Gold Mines may be upgraded to Alchemist Labs.
The cost to upgrade is one-half the current build cost. An upgrade takes approximately
half as long as building a new building.
You can see the status of upgrades by clicking on the My Status link in the left menu,
then on Construction Status.